MOSFETs and various methods of their manufacture are well known. Typically, a MOSFET includes source and drain regions at a surface formed in or on a suitable substrate, and a gate disposed therebetween. Silicide electrical layers or contacts are formed on the gate, and on the source and drain regions. In general, the typical known silicidation process is as follows: source and drain implants are done followed by a metal deposition and then an anneal to react the metal and implanted or doped silicon to form the silicide. Substrates include, for example, bulk semiconductor (e.g. silicon), silicon-on-insulator substrates (SOI), among other substrates. See, for example, U.S. Pat. No. 6,930,030 B2, METHOD OF FORMING AN ELECTRONIC DEVICE ON A RECESS IN THE SURFACE OF THIN FILM OF SILICON ETCHED TO A PRECISE THICKNESS, issued Aug. 16, 2005, by Rausch et al. which is hereby incorporated in its entirety by reference. FIG. 2M of the '030 patent, partially reproduced as FIG. 8 herein, shows a silicide layer/contact 54 disposed on a top surface of a polysilicon gate 44 of an nFET device 20 formed in an SOI substrate. Also shown are an oxide layer 42 disposed below the gate and spacers 48 disposed at sidewalls of the gate.
In CMOS technologies, nFET and pFET devices are optimized to achieve a required CMOS performance. Very different dopant species are used for nFET devices and pFET devices, accordingly. These species have very different physical properties such as a diffusion rate and a maximum activated concentration. In conventional CMOS technologies, the both nFET and the pFET usually share the same spacer process and topology. In order to optimize CMOS performance, the spacers typically can be of one maximum width and are designed to trade-off the performance between the nFET and the pFET. For example, if Arsenic and Boron are used as the source and drain dopants for the nFET and the pFET, respectively, it is known that a narrower spacer is better for the nFET but a much wider one is better for the pFET, because Arsenic diffuses much slower than Boron. In this case, the pFET is a limiting factor. Thus, the maximum width of all spacers is optimized for the pFET, trading-off the nFET performance.
It is also known to enhance performance of n-type field effect transistor devices (nFETs) and p-type field effect transistor devices (pFETs) by providing: tensile stresses to the channels of the nFETs and compressive stresses to the channels of the pFETs, and/or different spacer widths to control silicide distances from, for example, the channels.
See, for example, U.S. Pat. No. 6,869,866 B1, SILICIDE PROXIMITY STRUCTURES FOR CMOS DEVICE PERFORMANCE IMPROVEMENTS, by Chidambarrao et al., filed Sep. 22, 2003, issued Mar. 22, 2005; U.S. Pat. No. 6,890,808 B2, METHOD AND STRUCTURE FOR IMPROVED MOSFETS USING POLY/SILICIDE GATE HEIGHT CONTROL, by Chidambarrao et al., filed Sep. 10, 2003, issued May 10, 2005; and U.S. Pat. No. 6,806,584 B2, SEMICONDUCTOR DEVICE STRUCTURE INCLUDING MULTIPLE FETS HAVING DIFFERENT SPACER WIDTHS, by Fung et al., filed Oct. 21, 2002, issued Oct. 19, 2004, which are all hereby incorporated herein in their entireties by reference.
However, the present inventors believe that the methods and resulting device structures according to the prior art can be improved further, to provide both low and high performance devices of a same conductive type on a same substrate.